• International Journal of Fluid Machinery and Systems
• /
• v.3 no.4
• /
• pp.292-300
• /
• 2010

This study strives to develop an effective strategy to inhibit cavitation inception on hydrofoils by using local cooling technique. By setting up a temperature boundary condition and cooling a small area on the upper surface of a hydrofoil, the fluid temperature around the cooling surface will be decreased and thereby the corresponding liquid saturation pressure will drop below the lowest absolute pressure within the flow field. Hence, cavitation can never occur. In this paper, a NACA0015 hydrofoil at $4^{\circ}$ angle of attack was numerically investigated to verify the effectiveness of the proposed technique. The CFD results indicate that the cooling temperature and the cooling surface roughness are the critical factors affecting the success of such technique used for cavitation suppression.

• Journal of Bio-Environment Control
• /
• v.31 no.4
• /
• pp.286-291
• /
• 2022

The effect of root-zone local cooling on seedling growth of tomato was investigated. Lower pipe cooling was used for local cooling of the root zone, and the root zone temperature was set at 20 and 25℃. There was no difference in plant height, root length, and leaf number according to local cooling temperature. Leaf area, fresh weight, dry weight, and chlorophyll content of the shoot and root was higher in the 25℃ than those of 20℃ at 28 DAS. These results showed that cooling for seedling growth of tomato 25℃ is sufficient considering energy efficiency. This study will be helpful in the development of local cooling technology that can reduce the energy required for cooling during the production of tomato seedlings in the high temperature season.

• Journal of Dental Anesthesia and Pain Medicine
• /
• v.22 no.2
• /
• pp.87-96
• /
• 2022

This study aimed to assess the combined use of extraoral vibratory stimulation and extraoral cooling in reducing the pain (subjective and objective) of dental local anesthesia administration in children. PubMed, Cochrane Central Register of Controlled Trials, and Ovid SP databases were searched up to July 2021. Article titles were screened and full-text evaluations of the selected articles were performed. Finally, seven studies (391 children, aged 4 - 12 years) were included in this qualitative and quantitative analysis. The pooled data determined the combined effect of extraoral vibration and extraoral cooling as a single measure. Extraoral vibration or cooling alone were not compared. The measured primary and secondary outcomes were pain perception and subjective and objective pain, respectively. When compared with the control, extraoral vibration and cooling resulted in significant differences in the mean combined data for the variables, pain perception, and pain reaction. Children's subjective pain as measured by pain scores were reduced when extraoral vibration and cooling was used during local anesthesia administration (mean difference -3.52; 95% confidence interval [-5.06 - 1.98]) and objective pain (mean difference -1.46; 95% confidence interval [-2.95 - 0.02] ; mean difference -1.93; 95% confidence interval [-3.72 - 0.14]). Within the confines of this systematic review, there is low-quality evidence to support the use of combined extraoral vibration and cooling for reducing pain (subjective and objective) during intraoral local anesthesia administration in children.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.3
• /
• pp.419-430
• /
• 1999

Measurements of local blowing ratio and ammonia-diazo flow visualizations have been conducted for a shower-head film cooling on a first-stage turbine stator. In this study, six rows of normal holes are drilled symmetrically on the semicircular leading edge of a simulated blunt body. The measurements show that for an average blowing ratio based on freestream velocity, M, of 0.5, local average mass flow rate through the first two rows of the holes is less than those through the second and third two rows of the holes, and the fraction of mass flow rate through the first two rows to total mass flow rate has a tendency to increase with the increment of M. The flow visualizations reveal that the injection through the first two row results in inferior film coverage even In the case of M = 0.5, meanwhile the row of holes situated at farther downstream location provides higher film-cooling performances for all tested M. This is because film-cooling effectiveness depends on local mainflow velocity at the hole location as well as the mass flow rate through each row.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.1481-1486
• /
• 2004

This report presents experimental results on the heat transfer coefficients in the boiling region of spray cooling for actual metallurgical process. In this study, the heat flux distribution of a two dimensional dilute spray impinging on hot plate was experimentally investigated. Based on the experimental results, they classified the heat transfer area into the stagnation region and wall-flow region. In the stagnation region, the local heat transfer coefficient relates mainly to the droplet-flow-rate supplied from spray nozzle directly, so the local heat transfer coefficients is good agreement with the predicted values from correlation for spray cooling proposed by former report However, the local heat transfer coefficient in wall-flow region is larger than predicted values, and it is found that the rebounding droplets-flow-rate must be accurately evaluated to predict the local heat transfer coefficient in this region.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.12 no.10
• /
• pp.886-893
• /
• 2000

A good understanding of the heat transfer distribution is very important to suppress the deformation of steel products. In this study, the local heat transfer coefficients are experimentally investigated to understand the heat transfer distribution of thick steel plates with even flat spray nozzle. The steel slabs are cooled down from the initial temperature of about $1000^{\circ}C$ , and the local heat transfer coefficients and surface temperatures are calculated from the measured temperature-time history. The results show that the local heat transfer coefficients of spray cooling are dominated by the local droplet flow rate, and in proportion to becoming more distant from the center of heat transfer surface, the local heat transfer coefficients decrease with the decrease of the local droplet flow rate.

• Journal of Korea Foundry Society
• /
• v.17 no.6
• /
• pp.608-614
• /
• 1997

The effect of mold preheating temperature on the microstructure such as grain size, eutectic silicon morphology was investigated for the Al-7wt%Si-0.3wt%Mg alloy. Microstructural variations have been characterized as a function of Sr addition and cooling rate during solidification. Microstructures were correlated with cooling rate, local solidification time and eutectic nucleation temperature, etc. In this study, Sr addition caused increase of local solidification time, undercooling and reduction of eutectic plateau temperature. In logarithmic scale, local solidification time was in inverse proportion to cooling rate. Eutectic nucleation temperature was in inverse proportion to cooling rate of logarithmic scale. Increasing the cooling rate refined dendrite arm spacing and eutectic silicon. Dendrite arm spacing was logarithmically in inverse proportion to cooling rate. Without modifier addition, eutectic silicon was modified at cooling rate of $7^{\circ}C/s$ or higher.

• Fashion & Textile Research Journal
• /
• v.2 no.3
• /
• pp.265-271
• /
• 2000

Heat stress results in fatigue, a decline in strength, alertness., and mental capacity. The problem is compounded when high humidity exists. To help relieve worker heat stress, many types of cooling units are marketed. While workers may experience some cooling, critical body core temperatures often continue to elevate. This study was designed to find the effects of three kinds of cooling vest with portable frozen gel strips on thermophysiological parameters and on temperature and humidity within clothing. The heart rate, rectal, and skin temperature as well as sweat rate and clothing microclimate were measured during 80 min in 5 healthy males. Inquiries were also made into the subjective rating thermal, humidity comfort, and fatigue sensations. The main findings in our experiments are as follows: (a) Physiological parameters such as rectal temperature was the lowest in garb A1, intermediate in garb A, and the highest in garb A2 throughout the experiment. And mean skin temperature was the lowest in garb A, intermediate in garb A1, and the highest in garb A2; (b) Temperature and humidity within clothing (back) were garb in Al, intermediate in garb A, and the highest in garb A2. But the temperature and humidity within clothing (chest) were garb in A, intermediate in garb A1, and the highest in garb A2; (c) Most participants (4 out of 5 persons) answered that they felt more comfortable and fatigueless in garb A1 than in garb A and A2. It is concluded that local cooling in garb A1 of the upper torso could physiological reduce the thermal strain in participants wearing cooling vest.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.31 no.1 s.160
• /
• pp.119-130
• /
• 2007

The objects of this study were to investigate responses and peculiarity during local cooling by parts of the human body and to show permissible safety limits without injurious to his health because of excessive cooling when he works hot environments. It were measured rectal temperature, skin temperature, heart rate, total body weight loss, local sweat in back and thigh, clothing microclimate and subjective sensation on 8 subjects and cooling parts were head, neck, chest, abdomen, back, waist, hip, upper arm, forearm, hand, thigh, calf and foot. According to above-mentioned the first experiment, we chose permissible safety limits by parts of the human body for one hour. In the second experiment, it was showed permissible safety limits by parts which examined their safety about health through 4 hours cooling test on 3 subjects. The results are as follows: 1. As a result of the first experiment, we chose permissible safety limits by parts, as follows, head $25^{\circ}C$, neck $20^{\circ}C$, chest $27^{\circ}C$, abdomen $25^{\circ}C$, back $20^{\circ}C$, waist $20^{\circ}C$, upper arm $20^{\circ}C$, forearm $20^{\circ}C$, hand $23^{\circ}C$, thigh $20^{\circ}C$, calf $20^{\circ}C$ and foot $23^{\circ}C$ in $37^{\circ}C$, 50%R.H. environment for 1 hour. 2. As a result of the second experiment, cooling on these safety limits temperatures except chest didn't have a bad effect on health. So it was proved that right permissible safety limits of chest was $28^{\circ}C$. From these results, it has been suggested that skin temperature didn't fall below permissible safety limits when human body was to be cool by parts.

• Journal of the Korean Society for Heat Treatment
• /
• v.23 no.5
• /
• pp.249-256
• /
• 2010

Water jet impingement cooling has been widely used in a various engineering applications; especially in cooling of hot steel plate of steelmaking processes and heat treatment in hot metals as an effective method of removing high heat flux. The effects of cooling water temperature on water jet impingement cooling are primarily investigated for hot steel plate cooling applications in this study. The local heat flux measurements are introduced by a novel experimental technique that has a function of high-temperature heat flux gauge in which test block assemblies are used to measure the heat flux distribution during water jet impingement cooling. The experiments are performed at fixed flow rate and fixed nozzle-to-target spacing. The results show that effects of cooling water temperature on the characteristics of jet impingement heat transfer are presented for five different water temperatures ranged from 5 to $45^{\circ}C$. The local heat flux curves and heat transfer coefficients are also provided with respect to different boiling regimes.